Portable telephones, such as cellular telephones, must have a way of activating and deactivating the telephone. It is also desirable to make the telephone as small as possible. However, a certain distance between the earpiece and mouthpiece is useful to enable the telephone to extend from the user's ear to the user's mouth. Telephones, such as the Motorola flip-phone series, have conventionally pivoted into the open position to extend this distance. In addition, the telephone has often used the opening operation to control answering the call, and conversely used the closing operation to control ending the call.
Other systems are known which use a sliding portion. For instance, the Qualcomm sliding ear piece telephone allows the ear piece to extend. When the ear piece is down, however, the telephone is totally locked. It cannot make or receive calls, nor use any of the keyboard functions.